Print Report
A3328 Quercus garryana - Pseudotsuga menziesii / Toxicodendron diversilobum Forest & Woodland Alliance
Type Concept Sentence: This alliance covers savanna, woodland and forest dominated by Quercus garryana. Codominance by the evergreen conifer Pseudotsuga menziesii is common, and Pinus ponderosa can be important in some stands. This alliance occurs from southwestern British Columbia to northern California at lower montane on steep, rocky slopes where snow and cold temperatures occur.
Common (Translated Scientific) Name: Oregon White Oak - Douglas-fir / Pacific Poison-oak Forest & Woodland Alliance
Colloquial Name: West Cascadian Dry White Oak - Douglas-fir Forest & Woodland
Hierarchy Level: Alliance
Type Concept: This alliance consists of savanna, woodland and forest dominated by Quercus garryana. Codominance by the evergreen conifer Pseudotsuga menziesii is common, and Pinus ponderosa is important in some stands with mesic indicator species in the undergrowth. In the south, common associates also include Quercus kelloggii and Arbutus menziesii. The predominant oaks in areas of higher fire frequency include Quercus kelloggii and Quercus garryana, with Quercus garryana var. garryana codominant in the central and northern Coast Ranges. The perennial bunchgrass component includes Festuca idahoensis, Festuca californica, Elymus glaucus, and Danthonia californica (close to the coast). A variety of native forbs also occur. Other characteristic species include Toxicodendron diversilobum, Juniperus occidentalis, and Ceanothus cuneatus. This alliance occurs in southwestern British Columbia, in the Puget Trough and Willamette Valley south into the Klamath Mountains and into northern California, where it is found in the northern portions of the Sierra Nevada and Coast Ranges foothills at lower montane elevations from 600-1600 m (1800-4850 feet) on steep, rocky slopes where snow and cold temperatures occur. This alliance is associated with dry, predominantly low-elevation sites and/or sites that experienced frequent presettlement fires.
Diagnostic Characteristics: Dry low-elevation stands dominated by Quercus garryana which can have some Arbutus menziesii, Quercus chrysolepis, or Quercus kelloggii. Pseudotsuga menziesii is common, and Pinus ponderosa occurs occasionally but is not diagnostic. Other characteristic species include Toxicodendron diversilobum, Symphoricarpos albus, Juniperus occidentalis, and Ceanothus cuneatus.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This alliance concept parallels that of the ecological system ~North Pacific Oak Woodland (CES204.852)$$, where associations have floristic components of the west side of the Cascade Range and northern California. There is some floristic overlap with eastside white oak associations. Quercus garryana var. fruticosa (= var. breweri) associations are not included in this group or alliance. Several associations identified in California (Sawyer et al. 2009) are not included in those listed for this alliance, as they are not in the USNVC yet.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Broad-leaved deciduous trees ranging in density from very open savanna-like canopy to dense forest. Trees are from 15-30 m tall. Understory is usually herbaceous perennial graminoids; some stands have dense shrub cover.
Floristics: Vegetation within this alliance is characterized by a closed canopy of Quercus garryana, a winter deciduous tree, occasionally with scattered emergent individuals of Pseudotsuga menziesii or, less often, Pinus ponderosa. Acer macrophyllum is often an associated tree. There is often a tall-shrub stratum of Corylus cornuta var. californica, Amelanchier alnifolia, and/or Toxicodendron diversilobum. Many forb species can be found in these forests; some of the more common or important include Achillea millefolium, Apocynum androsaemifolium (= Apocynum pumilum), Brodiaea elegans, Camassia quamash, Fragaria vesca, Fragaria virginiana, Galium triflorum, Maianthemum stellatum, Osmorhiza berteroi (= Osmorhiza chilensis), Perideridia bolanderi, and Vicia americana.
Dynamics: Succession in the absence of fire tends to favor increased shrub dominance in the understory, increased tree density, and increased importance of conifers, with the end result being conversion to a conifer forest. Dry-season fire was historically common and controlled the abundance of invading conifers (Thilenius 1968). Quercus garryana is shade-intolerant and is eventually killed when overtopped by coniferous forest. Stands of this type often are seral to Pseudotsuga menziesii in the absence of fire (Chappell et al. 1997). Animal dissemination of acorns is important in dispersal of oaks and thus the presence of oak-dominated stands.
Environmental Description: Vegetation within this alliance is found in low-elevation (15-610 m) valleys and slopes of the Pacific Northwest, usually on the leeward side of the coastal ranges. This alliance is associated with dry, predominantly low-elevation sites and/or sites that experienced frequent presettlement fires. In the Willamette Valley, soils are mesic yet well-drained, and the stands are mostly large patch. In the Puget Lowland and Georgia Basin, it is found primarily on dry sites, typically either with shallow bedrock soils or deep gravelly glacial outwash soils. It occurs on various soils in the interior valleys of the Klamath Mountains, and on shallow soils of "bald hill" toward the coast. Even where more environmentally limited, it is strongly associated with a historic low-severity fire regime. With frequent annual burning (at lower elevations and on warmer sites), this is an open to dense woodland of large oaks with well-developed grassy understories of native perennial bunchgrass.
Precipitation ranges from 50-200 cm annually, with a decidedly warm, dry period in midsummer. Environmental factors that limit the invasion and increase of conifers play an important role in maintenance and functioning of these communities; foremost in importance are soil drought and fire. These communities are associated with excessively drained soils, or sometimes riparian areas and wetland transitions in prairie landscapes. Best stand development occurs on well-drained alluvial soils and mild slopes. This is one of the most drought-tolerant communities of the maritime Pacific Northwest.
Precipitation ranges from 50-200 cm annually, with a decidedly warm, dry period in midsummer. Environmental factors that limit the invasion and increase of conifers play an important role in maintenance and functioning of these communities; foremost in importance are soil drought and fire. These communities are associated with excessively drained soils, or sometimes riparian areas and wetland transitions in prairie landscapes. Best stand development occurs on well-drained alluvial soils and mild slopes. This is one of the most drought-tolerant communities of the maritime Pacific Northwest.
Geographic Range: This alliance occurs in southwestern British Columbia, in the Puget Trough and Willamette Valley and extends southward at low elevations in the Klamath Mountains on both sides of the Oregon/California stateline, and continues south in the northern portions of the Sierra Nevada and Coast Ranges foothills and lower montane of California and Oregon.
Nations: CA,US
States/Provinces: BC, CA, OR, WA
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899452
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: None of the old Quercus garryana alliances relate cleanly to this new alliance.
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: >< Quercus garryana (Oregon white oak woodland) Alliance (Sawyer et al. 2009) [71.030.00]
>< Oregon White Oak: 233 (Eyre 1980)
>< Western Broadleaf Forests: 26: Oregon Oakwoods (Quercus) (Küchler 1964)
>< Oregon White Oak: 233 (Eyre 1980)
>< Western Broadleaf Forests: 26: Oregon Oakwoods (Quercus) (Küchler 1964)
- Chappell, C., R. Crawford, J. Kagan, and P. J. Doran. 1997. A vegetation, land use, and habitat classification system for the terrestrial and aquatic ecosystems of Oregon and Washington. Unpublished report prepared for Wildlife habitat and species associations within Oregon and Washington landscapes: Building a common understanding for management. Prepared by Washington and Oregon Natural Heritage Programs, Olympia, WA, and Portland, OR. 177 pp.
- Evans, S. 1989a. Riparian survey of Washington''s Columbia Basin. Unpublished report prepared for The Nature Conservancy Washington Natural Heritage Program, Olympia, Washington.
- Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.
- Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
- Franklin, J. F., and C. T. Dyrness. 1973. Natural vegetation of Oregon and Washington. General Technical Report PNW-8. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, OR. 417 pp.
- Küchler, A. W. 1964. Potential natural vegetation of the conterminous United States. American Geographic Society Special Publication 36. New York, NY. 116 pp.
- Sawyer, J. O., T. Keeler-Wolf, and J. Evens. 2009. A manual of California vegetation. Second edition. California Native Plant Society, Sacramento CA. 1300 pp.
- Thilenius, J. F. 1968. The Quercus garryana forests of the Willamette Valley, Oregon. Ecology 49:1124-1133.